Glioblastoma (GBM) is one of the most lethal of all cancers. As such, new therapeutic strategies are desperately needed. We and others have shown that metabolic reprogramming is a key feature of GBM to accommodate the heightened energetic, nutrient and redox requirements to support tumor growth and survival. The most prominent characteristics of this metabolic reprogramming are a shift to high glucose metabolism. Recent evidence suggests that oncogenic signaling regulates glucose utilization in GBM. Accordingly, inhibition of oncogenic signaling can disrupt glucose metabolism, leading to reduced metabolic intermediates for cellular energetic and anabolic processes. However, the therapeutic potential of targeting oncogene-regulated glucose metabolism in GBM remains enigmatic. We present compelling preliminary data demonstrating that acute inhibition of EGFR ? the most frequently altered oncogene in GBM - can rapidly and potently attenuate glucose uptake and consequently glucose metabolism in patient-derived GBM models. As a result of this ?altered? metabolic state, GBM models show synergistic intrinsic apoptosis to pharmacological p53 activation. We also demonstrate that 18F-flurodeoxyglucose (FDG) and positron emission tomography (PET) can be used as a rapid (within hours), non-invasive biomarker that may predict sensitivity to this new rational combination. In this revised R01 application, we extend on these exciting preliminary studies and investigate in Aim 1 the precise signaling and metabolic mechanisms whereby EGFR inhibition sensitizes GBMs to p53 activation. In Aim 2, using established BH3 profiling technology, we propose to characterize the pro- and anti-apoptotic signatures resulting in p53- dependent lethality following inhibition of EGFR-regulated glucose metabolism. Finally, in Aim 3 we will determine whether combined targeting of oncogene-regulated glucose metabolism (e.g., with EGFRi) and pharmacological p53 activation (in collaboration with Roche) is efficacious in direct-from-patient orthotopic GBM xenografts. We will also evaluate whether 18FDG PET can serve as a robust non-invasive biomarker for quantifying rapid changes in glucose metabolism with EGFRi via a pilot clinical trial in molecularly enriched recurrent GBM patients. The studies proposed in this application present a new combination strategy, coupled with a non-invasive predictive biomarker, aimed for specific manipulation of metabolism and apoptotic pathways in malignant glioma and have the long term potential to shift current approaches in glioma therapy.